dietzsch



March l5, 1932. F. DIE-rzscH WET EXTRACTION 0F COPPER Filed July 19, 1928 ATTORNEY Patented Mar. 15, 1932 l ED; ,STATES mann:NAND DIE'rzscnr or xiNesron-oN-Tnniuns, Encamp l y 1 u Application-median 19; 192s, serial No. zsaossfaiiaiiiereat Britain sepi'emteraa, 1927. l

Y' It is now well known in the wet metallurgy of' copper that the. extractionlo ,the metal values from oxide or oxidized copper ores n by means of Ihydrochloric acid or sulphuric 5 acid is far less satisfactory than ,that obtainable bymeans of a leaching liquor consisting ofa somewhat1concentrated solution ofa metal chloride containing sulphur dioxide. i Whilst'a'solution of a chloride containing '10 sulphurV dioxide -is an effective reagent; for

chloridizing copper, it is not, whenof moderate concentration, a remarkable solvent for V-the chloridized copper, and it therefore is y necessary to use either a large bulkY ofleachv1`15-ing liquor Vor to use aA concentrated solution ofthe chloride. Thus solutions :of-sodium' chloride of per cent. strength and even saturated.solutions'have'been specified. The l use of concentrated solutions, however, means Y 2'0 either a loss of material in the tailings remaining associated with the leached ore after this has been drained` or if attempt is made to recover this material bywashing` a relatively expensive step `is introducedyinto'the f" 2`5 process by the necessity for concentrating the v'diluted' washings.A L f e ..1

Y I have found ythat the foregoing disadvantages fare avoidedif'. the metal chlorideY is wholly orl partly replaced by hydrogen chlosorride and'that operation in a cyclic process is simpliied, provided that the-copper ius-precipitated from the spent leachingliquorby `Ameans of la reagent which regeneratesthehye drochloric acid consumedl inthe extraction, 5 namely by means of sulphuretted hydrogen'.

OneV advantageofY the invention lies'finthe 4:tact that hydrochloric acid is amuch better solventfor. the chloridized copper, so that o the chlorine ion can be considerably less than rwhen a metal chloride alone is used. Hence the quantity-,of material remainin'gin the tailings is small and its recovery is not a difi'cult matter.' By the process of this invention it becomespossible to treat materials rich in copper, such as rich roasted flotation concentrates, economically by the agitation method, a procedure which in the known method using f solutionr of 1 a metal chloride li'nvolvesthe diiiculties alreadyindicatedowing tothe moderate solvent powerffh Y liquorfor'thechloridizedjcoppen L v l Another important YadvantageI of` the. `new process-is that the consumptionzof sulphur dioxide is lower-than in the knownprocess wherein this reagent is usedinvconjunction with a solutionof a meta-l chloride. Inthe Y known process sulphuric acid formed by the reducin actionof sulphurV dioxide onthe ore is fixed 1n the formof Ametal sulphate,which t t means that a certain quantity of'metall chloride 1s consumed duringdeach leachingoperatlon -andconverted into materials' of no lvalue vas far as the processisgconcerned. `Also any acid-consuming materials inthe ore aref-de- US .stroyed'at the expense ,ofsulphur Vdioxide, a a part of which is therefore uselesslylconsumed., I have found, however, that the effect offusingga liquor containing vhydrochloricfacid Vis that sulphuric' acid formed vbyaoxidation 17o of sulphur dioxide during the leaching does not becomexedas 'sulphate by reactionl with metal? chlorideV when this, is present together with; hydrochloric acid; alsothat thisisullrphuricacid isgconsumed in preferencetosul phur dioxide bymaterialssuchas carbonates -inthe ore readily attacked by acid. -Exactly lwhat reactions occur I am not prepared to say, but the net-result is that acid-consuming materials are destroyed at the expense of theilio sulphuric acid formedfby the reduction of the copper 'by means ot sulphur dioxide, in-

stead of ,byfai quantityl of sulphurous'-vaacid` additional to that consumed inrejducing the @Opperfas in the known process-1, i Hensethelf's zprocess involves aneconomy insulphur dioxy n ide., A

`111malso ratifiant the' ,eeiiceiaifiiqn'b'f Sulphr dioxide in 'the new' process needing; .I 'be so high @sin the kIiOWnprocess.4 y f -f u It will be understood hat, as 1n he known process using a chloride solution together i l'with sulphur dioxide, Athe presence ofsulphur dioxide during the extraction is 1an essential condition. The treatment ofcopper vores with "05 an acid chloride'or other 'acid solution and theA u reduction of the dissolved copper-` to'the cuprous state :by subsequent treatment of the extract with sulphur dioxide asa-preliminary l to precipitation of 'thecoppe-r ,by hydrogen 2100 sulphide is known in the art, but'the results attained by this treatment, in which sulphur dioxide is absent during the extraction, are far from satisfactory.

. The accompanying drawing is a flow sheet of the process described herewith.

Generallyv the'l process starts with sodium chloride", onothermetal chloride, to' avoid importation of hydrochloric acid. ..intothe works.' Y When the material tobe' treated contains sulphur dioxide and has thereforeto be-roast-` ed as a preliminary, the sulphurdioxide obtained generallysuiicesnot onlyy for.Trunk-ingr,Y

up, the leaching liquor but for providing the eulph-urette'dvv hydrogen, forwhich purpose it may bepass'edogether with steam, over heat'- dffcarboni Suche@ through a! gasy producer. "remue chloride is; armed inf the @ir-eue@- flturf, which? is no disadvantage,'s`i`nce it is newntdbean excellent selventef oxidized su-lphuretted hydrogen by v reaction" with t ferrous sulphide oifoth'er sulphidei-n known o I1 have" found, howeventhatat is idea s ff pyrit'es and limev suitableproportiong fw chinaylbfe a's high as 2 parts' oflpyritesto V Y part of lime;l 'lSuch-"a'J mixture is readily *attacked by" relatively' dilutea'cid, the sul?- 'phuretlted hydrogen `is used for' precipitation "zhneV next batch ref cop-per liquer while'the A:fe'r'frius'chloride, or other chloride, liquor' is `Yretu'rnedtdthe-leachingvat l v-f In'one mode 'of carrying out the invention the "groundniaterial is leached systematical- 'l`y' in known manner with a .saturated solution .Liefcemrnenj seltwhic'hhasbeensaturated with sulphur' dioxide while exposed to the atmos- 'ihere..A The liquor 'from the last leaching vat of heseri'es (in) which ithasspent its content sldlnu"l dioxideV on fresh oret or haslost l ntent' by action of heat) i'sjrun'into a tank aiidvth'roug-h it Vis'V passed acurrent'of y gases containing sulphuretted hydrogeny'or allowed tosprinkle ldown a tower in counter-'currentn to the"A gases. Y A :cuprous sulphide is settled'andthe'clea'r 'liqf The precipitated is returned .to the sulphur dioxide satur-v .atingapparatuswhenceitenters the leaching lg'systemagain, but thistime containing hydrochloric acid inplaceofsomeof the common salti [Itisggsometimesconvenient to dispense "witha separate sulphurl dioxide 'saturator `and V f'ft introduce sulphur dioxide 'into-a mechan-V ical-ly Vagitated leaching Vvessel or together wth air blown linfor' producing agitation.

"e'ous'to' generateV artificially' aV sulphide imxturebyfusingor fri-tting a'mixt'ure p The following examples illustrate the invention Example 1.-A Chilean oxidized copper ore containing mainly carbonate and oxide ofl copper, together with silicate of copper, disseminated in a gangue partly soluble in acid, 1 1

was crushed to 1A] size;

rl'wo portions of the crushed each vats A` and B., The tops of these vats were weighing 300 kilos and assaying 3.6 per cent. of. Copper,Y were placed` on filter beds resting on' false' bottoms in two rhard wood leaching covered by'light sheets of tarpaulin tightly ii-xedf'to preventthe escapegof. gaseslduring the The inner surfaces ofk leaching operations. the' vatsfwere' covered? with` albituminous compound having a high melting"point,forprotection against acid..

' The leaching solution consisted-@537775:

of.'- sodiumv chloride'solution off-per.` cent.

strength, which was charged. with .sulphurou's' acid by passing through itvair. containing 3 per. cent. ofsulphur dioxide." f fz The charged' solution was allowed Ltopercolate' eight times in 48 hoursthroughthe ore in! vat A.. The iiow ofthe solution was fregl'ilated by. means of a stop-cock. rThe sul.- p'hl'ir'o'usr acidcontent of thefsoliltior'lA was -broughtupto full strength after each pcrcolation by:v ive-charging it with. sulphur dioxide before. allowing it to` come again intojfcontact witlithe ore; The: solution wast finally made to pass loncefthrogh the" fresh. ore:v in

vat B. InV that manner ythe excess of sulphur dioxide v"was" eliminated by allowing ity -to 'spend itselfin dissolving 'copper fromifiesh one?" v f :,rVV

The orev resid-ue' in v'at with a quantity' of sodium chloridefsol-ntion acid, to remove the dissolvedicppervalues adherinfgto the ore whichwas thenlallowed to f drain; l The amount ,of solution still-'retained water equivalent' in quantity to the' retained solution.' .i After this treatmentthe'` quantity of copper found inthe residual'ro're inVatAshowe'dthat an extraction of 95.83 per cent,v ofthe total originalzcopper values-,had been obtained."

bythe'residuey was then ascertained and; was -displ'acedby percolating throu'gh the-.fiore 1 The dissolved copperv in the leaching liquor and ,washings was precipitated' "passing Y @through theliquid a gas mixture containing hydrogen sulphide and made by passing sul- Vphurdioxide, ail` and steam through glowing lcokev vcontained in heated.

jnuiron'fube' externally After'the precipitation of the Opper'f the solution was found to contain 1.2p'e'r cent.

of Afree acid calculated .as hydrochloric vacid as well ferrous chloride `and other chl'o- Y rides;

'f'lfhis acid solution wasnext Yto'lcornv"plete the treatment of'rthefore -in-vatB in of 8 per cent. strength, free from sulphurous 05 exactly the same manneras described for vat A, except that they 37 5 litres of solution were `passed through the ore eighttimes in 4:4:

. cupricv chloride to cuprous chloridebyv the action of sulphurous acid, is apt to accumulate. This acid is economically eliminated by using it to generate hydrogensulphide from a mixture of ferrous and calcium sul# phides made by melting say three parts of lime with 10 parts of pyrites. Y f

, Togenerate hydrogen sulphide from such a mixture of sulphides, however, requires' a -sulphuric acid of about 5 per cent. strength, which is a stronger concentration than is Vat first obtained in the leaching solution. This requisite concentration of acid can be 0btained by the addition of acid from an extraneous source or can be automatically built up by at first precipitating the copper with'- hydrogen sulphide. `this being made bypassing sulphur dioxide, air and steam through glowing coke. After a few cycles of operationV the sulphuric acid will have beenV brought to the necessary-strength. Having, once obtained this concentration of acid, the

major part of the hydrogen 'sulphidecan be continually generated from the sulphide mixture by the acid in the solvent solution, pro'-l vided the copperin part of the solution is precipitated Vwith hydrogen sulphide generated otherwise. This is a distinct advantage as the generation from the sulphide mixture in many localities is considerably cheaper.

The whole of the hydrogen sulphide cannot be generated' fromV the sulphide mixture as some of the acid is lost 'by adhering toV the acid.

which assayed 14.37 per cent. copper, was crushed toV pass a l mesh sieve and was then roasted to prepare it for leaching.v The gangue soluble in acid in the'roasted product was small. v

Hard-wood vats such as are described in Example l were iilled each with 300 kilos of the roasted product. y

The leaching solution was one that was originally sodiumchloride solution of 8 per cent. strength, but owing to repeated use as solvent its sodium chloride content had been converted in part into 'other chloridesespecially ferrous chloride. It also contained 5 1.65 per cent. of free hydrochloric acid and A Queensland copper ore consisting almost entirely of sulphides of copper and iron and Y :acidfi- -v U p The ore pulp was introduced into-anllja'gif y tator tank of the Pachuca type'internally pro-i.

f its'A sulphuric acid `V concentration ','hadfbeen i l built, up 15o-.528 .cent..by. repeatedprecipitations ofcopperfromfit by hydrogen ysulphide lsgenerated,by passing sulphur dioxide, air Vandsteam over .glowing gcoke, L The solution -ou'tletof` vatuA was adjusted :in such manner as t0` 1allow?1,600.litres. .olf

solution ztap'ercolate,eight timesgthrdugh'the ioreainAOhours.; Thecopperfcontent ofthe residue -show' d that,}94.5 fperlcient'.i Qf-Qth'e .75

coppe-r in the rehad lbeen extracted. s l, As vin VExfmiple lathe Copper vSolution was freedfrom acid'byjpassing it through the fresh` ore ini vat B, andl its 'copper' contentV content @equivalent `ton ,per .c ell'.-` hydrochloric acid. was. usedV ,to'zattacklthe f mixture of iron and' lime sulphides in .order to Vgen- ,n g5 l serate hydrogen sulphide Vfor the precipitationof the copperfrom the neutralsolution 1 obtained. in the treatment, of, another. batch of ori-5.1.A It was found that'the-,acid generated .was .not quite `sufficient for 'the preparation y' 90 ofk the necessary hydrogen sulphide and yto overcome this 20 percentof the solution was separated from the Vmain.bulkja-nd its copper fcontent, .precipitated -by .hydrogen sulphide genera-tedv by blowing, sulphur dioxide,"`air;-

Vand steam' throughfredr hot` coke. {After settlingthe copper sulphide and eliminating the excess `of hydrogen sulphide inthe solution Y by theaddition ofasuiiciencygof cuprifer'oussolution, by heatingit, orv by `passingsulphurr',.e100`v zdioxide :through it', the lsolution 1 wasvagain :ready vfor leaching i.another-Iy batchof ore. LThusjthe processfbecomescyclic.

E'ample quantity. of fflotationiiconf acentratesf. was roasted in a'mannervvhich en-iflOB y sured goodleaching extractions and was then found to assay 20.9ipercentof copper.

Of' this roasted'product' "300 kilos were mixed withl 1125 litres'4 of a, chloride solution which hadforiginally :beenl a .saturated solullo U .tionlof sodium chloride,butfafterrepeatedlv tailings and by dissolving gangue soluble in using it' for leaching vthels'am'e product, `Tit v had "becomega mixture'foff -ferrous',fsodium and other chlorides land-falso? containediZjSYp-er cent.` of free *acidl i centext'raction had been obtained. Y 

